#pragma GCC target("avx2")
#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define ALL(a) a.begin(), a.end()
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using mint = atcoder::modint998244353;
istream &operator>>(istream &is, mint &a)
{
	int t;
	is >> t;
	a = t;
	return is;
}
ostream &operator<<(ostream &os, mint a)
{
	return os << a.val();
}
#endif
typedef long double ldouble;
#undef long
#define long long long
#define vec vector
template <typename T>
ostream &operator<<(ostream &os, vector<T> &a)
{
	const int n = a.size();
	rep(i, n)
	{
		os << a[i];
		if (i + 1 != n)
			os << " ";
	}
	return os;
}
template <typename T, size_t n>
ostream &operator<<(ostream &os, array<T, n> &a)
{
	rep(i, n) os << a[i] << " \n"[i + 1 == n];
	return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &a)
{
	for (T &i : a)
		is >> i;
	return is;
}
template <typename T, typename S>
bool chmin(T &x, S y)
{
	if (x > (T)y)
	{
		x = (T)y;
		return true;
	}
	return false;
}
template <typename T, typename S>
bool chmax(T &x, S y)
{
	if (x < (T)y)
	{
		x = (T)y;
		return true;
	}
	return false;
}
template <typename T>
void operator++(vector<T> &a)
{
	for (T &i : a)
		++i;
}
template <typename T>
void operator--(vector<T> &a)
{
	for (T &i : a)
		--i;
}
template <typename T>
void operator++(vector<T> &a, int)
{
	for (T &i : a)
		i++;
}
template <typename T>
void operator--(vector<T> &a, int)
{
	for (T &i : a)
		i--;
}
#undef endl
#define endl '\n'
void solve()
{
	int n, m;
	cin >> n >> m;
	if (n == 1)
	{
		cout << "No" << endl;
		return;
	}
	int s, t, k;
	cin >> s >> t >> k;
	s--, t--;
	vec<vec<int>> g(n);
	rep(i, m)
	{
		int a, b;
		cin >> a >> b;
		a--, b--;
		g[a].push_back(b);
		g[b].push_back(a);
	}
	vec<int> d(n);
	constexpr int inf = 1e9;
	vec<int> dist(n, inf);
	queue<int> q;
	q.push(s);
	d[s] = 1;
	dist[s] = 0;
	while (!q.empty())
	{
		int v = q.front();
		q.pop();
		for (int u : g[v])
		{
			if (d[u] == 0)
			{
				d[u] = -d[v];
				dist[u] = dist[v] + 1;
				q.push(u);
			}
		}
	}
	if (k % 2 == 1)
	{
		if (d[t] == 1)
		{
			cout << "No" << endl;
			return;
		}
		if (dist[t] <= k)
		{
			cout << "Yes" << endl;
			return;
		}
		cout << "Unknown" << endl;
		return;
	}
	if (d[t] == -1)
	{
		cout << "No" << endl;
		return;
	}
	if (dist[t] <= k)
	{
		cout << "Yes" << endl;
		return;
	}
	cout << "Unknown" << endl;
}
int main()
{
	// srand((unsigned)time(NULL));
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	// cout << fixed << setprecision(40);
	int t = 1;
	// cin >> t;
	while (t--)
		solve();
	return 0;
}